A comparative study of the larval development of Monodaeus couchi (Couch), Xantho incisus Leach and Pilumnus hirtellus (Linnaeus) (Crustacea: Brachyura: Xanthidae)

Summary

Comparative accounts are given of the larval and first crab stages of three crab species belonging to the family Xanthidae: Monodaeus couchi (Couch), Xantho incisus Leach and Pilumnus hirtellus (Linnaeus). Features are discussed that distinguish the larvae of these species from those of other N.E. Atlantic brachyrhynch crabs.     

The larval and post-larval development of Gibbs's spider crab,Pisa armata (Latreille) [family Majidae: subfamily Pisinae], reared in the laboratory

Summary

The larvae and first crab stage of the spider crab Pisa armata are described from laboratory reared material. The larval stages are compared with previous accounts and with those of Pisa tetraodon. Larval affinities with other genera of Pisinae are discussed.     

The complete larval development of the crab Pilumnus spinifer (Brachyura: Xanthoidea: Pilumnidae) reared in the laboratory

The complete larval development of the crab Pilumnus spinifer from the western Mediterranean was obtained in the laboratory. All four zoeal stages and the megalopa are described and illustrated. The morphological characters of the larvae of Pilumnus spinifer are compared with those of other known larvae of the genus. The zoeae of P. spinifer show the rostral spine longer than the antennule (excluding aesthetascs); short lateral spines present on the carapace, and the mediolateral processes are present only in abdominal somites 2 and 3. The megalopa is similar to that of other Pilumnidae species. The morphology of the larval stages shows very similar characteristics to that of those of P. hirtellus and P. dasypodus, among the described stages of the family.     

Taxonomy and ecology of the porcellanid crab Polyonyx cometes Walker, 1887 (Crustacea: Decapoda), with description of a new genus

The taxonomy of the rare porcellanid crab, Polyonyx cometes Walker, 1887 (Crustacea Decapoda), is reconsidered in the light of fresh material from Singapore, as well as the newly obtained first zoeal stage. Polyonyx cometes possesses numerous adult and larval characters which warrant the establishment of a new genus for the species. The species is confirmed as a commensal of the worm Chaetopterus (Annelida, Polychaeta).     

Taxonomy and geography of the blackflies of the Canary Islands (Diptera: Simuliidae)

The Canary Islands provide a difficult habitat for Simuliidae because of the scarcity of running water for the early stages, but the archipelago currently supports a fauna of six species (one other species formerly present is considered extinct). Breeding is confined to three of the seven islands (Gomera, La Palma, Tenerife), but once occurred also in Gran Canaria, an island that now lacks flowing streams. The taxonomic and faunal conclusions are based on a study of all available specimens, including material of early stages and reared adult flies collected by the author and aided by cytological data from the larval polytene chromosomes of several species. Twenty-one nominal species have at some time or another been reported from the Canaries, but, following this revision, only seven are recognized in the fauna (most past records being erroneous and based on misidentifications or false assumptions of endemicity); full synonymies clarify the old records in relation to modern nomenclature. All species belong to Simulium Latreille s.l., and keys are given to them in adult, pupal and larval stages. Three species are endemic (two newly described) and the other four common to the Palaearctic mainland. Some remarks are included on simuliid colonization and extinction in the islands.     

Studies on the provenzanoi and other pagurid groups: VI. Larval and early juvenile stages of Pagurus ochotensis Brandt (Decapoda; Anomura; Paguridae) from a northeastern Pacific population,reared under laboratory conditions

Zoeal, megalopal, and early juvenile stages of Pagurus ochotensis (Brandt, 1851) from a northeastern Pacific population are described from laboratory-reared individuals. Zoeal and megalopal development in this population is compared with that described for a population of this species from Hokkaido, Japan. First and second juvenile crab stages of this species are described for the first time. The nearly identical developmental morphology of the two populations supports the earlier synonymy of the northeastern Pacific species, Pagurus alaskensis (Benedict) with P. ochotensis.     

Larval development and emigration behaviour during sea-to-land transition of the land hermit crab Coenobita brevimanus Dana, 1852 (Crustacea: Decapoda: Anomura: Coenobitidae) under laboratory conditions

To determine the early life history of the land hermit crab Coenobita brevimanus Dana, 1852, larvae were cultured individually in the laboratory. The zoeal and the megalopal stages are described and illustrated. The larvae developed through four planktonic zoeal stages to the megalopal stage. The major differences in the zoeal characters between C. brevimanus and other described Coenobita species were found in the armature of the pleomeres, whereas the character of pleomeres of C. brevimanus zoeae is the same as that of the coconut crab Birgus latro, a different genus in the same family. Morphological similarity was also found in segmentations of antennules and antennae in megalopae between C. brevimanus and the coconut crab. Megalopae of C. brevimanus were cultured in containers holding seawater and a hard substrate. These crabs migrate from the sea to land after developing a habit of acquiring gastropod shells.     

The complete larval development of Sadayoshia edwardsii (37) (Decapoda: Anomura: Galatheidae) described from laboratory‐reared material

The complete larval development of Sadayoshia edwardsii (Miers, ) is described and illustrated from laboratory‐reared material. The development comprises four zoeal and one megalopal stages. Diagnostic zoeal characters of Sadayoshia are provided and these are compared with other galatheid genera for which the larval morphology is known. Zoeas of S. edwardsii are readily distinguished from those of other galatheid species by the setation of the maxillular endopod together with the basis and endopod of the first maxilliped. The megalop of S. edwardsii has a flattened, triangular‐shaped rostrum, which differs remarkably from that of the adult. Although the rostral shape resembles that of Galathea megalops, the armature of the lateral margins is different between megalops of the two genera. The present larval study suggests that Sadayoshia is more closely allied to Galathea than to Munida.     

Larval development in Phimochirus roseus (Benedict) (Decapoda: Anomura: Paguridae) reared in the laboratory

The zoeal and megalopal stages of Phimochirus roseus (Benedict, 1892) are described and illustrated from material reared under laboratory conditions. Although the vast majority of zoeae of this species pass through only four larval stages before the moult to megalopa, an occasional fifth stage has been observed. Phimochirus roseus differs in a number of morphological attributes from the only other species of Phimochirus whose larvae have been described. However, their shared features are sufficiently characteristic to confirm the distinctiveness of the genus and its general developmental homogeneity.     

Description of the first larval stage of Polycheles typhlops (Decapoda: Eryonidea: Polychelidae)

The first larval stage of the deep-sea lobster Polycheles typhlops is described for the first time from laboratory-reared material. This is the earliest stage known of the Decapoda infraorder Eryonidea, and the first stage ever obtained in the laboratory. The first larva of P. typhlops presents well-developed and chelated pereiopods I and II; the abdomen is very small and not well segmented; the pleopods and uropods are represented as small buds. Larval features of the first stage of P. typhlops are compared with other known eryoneicid forms described in the literature, especially with specimens in early developmental stages taken from plankton samples.     

Larval release rhythms of four species (family Grapsidae and Ocypodidae) of intertidal crabs on a coastal flat in western central Taiwan

Larval release rhythms of four crab species, Parasesarma tripectinis (Shen, 1940), Perisesarma bidens (De Haan, 1835), Hemigrapsus penicillatus (De Haan, 1835) and Baruna sinensis Tan and Huang, 1995, were studied in two different intertidal zones on a coastal flat. Of these, P. bidens is the only species that migrates between high and lower intertidal zones. In general, larval release patterns of these intertidal crabs are not too different from those of intertidal crabs living in other geographical regions, which often release larvae around new or full moons and nocturnal high tides. However, differences were apparent when compared with previous studies in that: (1) peak larval release periods of P. bidens occurred during submaximum tidal amplitudes, (2) a good portion of B. sinensis released their larvae during neap tides, (3) all four species released their larvae during both daytime and nighttime high tides although the percentage varied among these species, (4) three species released their larvae within 1 h after the time of high slack tide, but larval release of B. sinensis peaked between 1 and 2h after the time of maximum tidal height. Larval release pattern of Perisesarma bidens suggests that locomotory behaviour of high intertidal crabs may influence their larval release rhythms. Antipredatory adaptation may explain larval release rhythms of the four species examined in the present study. Larvae of Parasesarma tripectinis, P. bidens and Hemigrapsus penicillatus are more vulnerable to planktivorous fish predation and tend to release their larvae at nocturnal high tides during maximum tidal amplitudes. On the other hand, larvae of Baruna sinensis may be better adapted against planktivorous fish predation by having yellow-green colour. The timing of larval release of this species occurred throughout the lunar cycle and often at daytime 1-2 h after the time of high slack tide.     

Abbreviated larval development of the freshwater prawn,Macrobrachium pilimanus (De Man, 1879) (Decapoda,Palaemonidae), reared in the laboratory

The larvae of the freshwater prawn, Macrobrachium pilimanus (De Man, 1879), were reared in the laboratory. Larval development was highly abbreviated, with two zoeal and one megalopal stages. Newly hatched larvae were benthic, with a tendency to cling on to roughened surfaces. All larval stages subsisted solely on endogenous yolk. Morphological and behavioural differences between the first zoea of this species and that of M. malayanum (Roux, 1934) are highlighted. The potential use of larval characters in taxonomy is also discussed.